We propose to collect 20ml of blood from 40,000 persons in Washington County, MD from May through October 1989, and to store plasma and white blood cells from those persons at -73 C. In addition to basic identification and personal information obtained when blood is drawn, participants will be asked to complete dietary questionnaires at their leisure and to return them along with a toe nail clipping for trace metal analyses. Blood pressure readings will be taken on participants, primarily as a service to them. The basic personal information and the blood pressure results will be analyzed for the entire study population. Dietary histories and information from plasma, white blood cells, and toe nails will be analyzed for limited nested case-control studies of specific cancers as these develop among participants and are identified by our cancer registry. Examples of potential cancer risk factors include vitamins (A, D, E, carotenoids), trace elements (selenium, zinc), hormones (estrogens, androstenedione, progesterone, prolactin, luteinizing hormone, testosterone, ect.), lipids (plasma cholesterols, lipoproteins), white blood cell components (DNA adducts), and antibodies (herpes, cytomegalovirus, papillomavirus, Epstein-Barr virus). Comparisons between intake as estimated from questionnaire data and serum levels of various nutrients can be made. Representativesness of the participants in the program will be assessed by comparing the characteristics with those who reside in Washington County with the characteristics recorded in the 1990 Census. Records from the current project will be linked with those from the 25,602 persons who gave blood to a serum bank in 1974, allowing thereby an assessment of repeatability of findings over time. Because there is almost no definite information on such fundamental factors as stability of plasma components on prolonged storage or on repeated thawing and freezing, plasma from participants who do not live in the immediate area of Washington County will be used to study the stability of vitamins, hormones and lipids.